Mexico, officially the United Mexican States, is a federal republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of Mexico. Covering almost two million square kilometres, Mexico is the fifth largest country in the Americas by total area and the 13th largest independent nation in the world. Mexico is a federation comprising thirty-one states and a Federal District, its capital and largest city.
In pre-Columbian Mexico many cultures matured into advanced civilizations such as the Olmec, the Toltec, the Teotihuacan, the Zapotec, the Maya and the Aztec before first contact with Europeans. In 1521, the Spanish Empire conquered and colonized the territory from its base in Mexico-Tenochtitlan, which was administered as the Viceroyalty of New Spain. This territory would eventually become Mexico following recognition of the colony's independence in 1821. The post-independence period was characterized by economic instability, the Mexican-American War that led to the territorial cession to the United States, the Pastry War, the Franco-Mexican War, a civil war, two empires and a domestic dictatorship. The latter led to the Mexican Revolution in 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the country's current political system. In March 1938, through the Mexican oil expropriation private U.S. and Anglo-Dutch oil companies were nationalized to create the state-owned Pemex oil company.